Fish farming is a large business but the damage caused by parasites cost fish farmers huge sums of money each year. Chemical treatments (see, e.g., U.S. 2013/0095126, incorporated herein by reference) may be ineffective and/or costly, may damage or kill the fish, and/or may pollute the water and/or damage other organisms. Certain pesticides, drugs, vaccines, and the like may result in genetically resistant sea lice.
Warm water and/or fresh water treatments may be ineffective, expensive, and often require long treatment times. Moreover, if the sea lice become resistant to fresh water, then wild saltwater fish migrating in fresh water can be put at risk.
Some mechanical treatments have been proposed. For example, WO 98/24314, incorporated by reference herein, proposes using water jets to remove sea lice from salmon. But, the water jets are fixed in place. Since the salmon are not stationary, and are not a constant size, large fish may be damaged by the water jets and, for smaller fish, the jet pressure may not be great enough to effectively remove the sea lice. Moreover, the water from the spray nozzles has to travel through water before reaching the surface of the fish body lowering the effectiveness of the water jet. And, the water jets are in a single fixed configuration with fixed angles.